A 15-year-old high school student uses a vaping device near the school’s campus in Cambridge, Mass.

—Steven Senne/AP

New York

Vaping held steady last year in high school students and declined in middle school kids, according to new government data, but some researchers are skeptical because the survey may have missed out on a booming e-cigarette brand.

The Centers for Disease Control and Prevention survey did not specifically ask about Juul e-cigarettes, and research suggests some kids don’t equate the trendy devices with other types of e-cigarettes.

Given that omission and the skyrocketing sales of Juul last year, the survey may be missing a big part of what’s going on, said Jidong Huang, a Georgia State University researcher.

E-cigarettes are battery-powered devices that provide users with aerosol puffs that typically contain nicotine, and sometimes flavorings like fruit, mint, or chocolate. They’re generally considered a less dangerous alternative to regular cigarettes, but health officials have warned nicotine is harmful to developing brains.

The new CDC study is based on a questionnaire filled out annually by roughly 20,000 students in grades 6 through 12. The study focused on “current users”—defined as kids who said they had used a tobacco product in the previous 30 days.

The CDC survey, and others, have shown a general decline in the use of tobacco products.

But the level of vaping soared until 2016, when there was a puzzling and dramatic drop, from 16 percent to 11 percent of high school students. That translated to a decline in teen vapers from 3 million to 2.2 million in just one year.

Experts at the time attributed the decline to public health warnings, sales restrictions, and the possibility that fewer kids saw e-cigarettes as being novel.

Vaping devices that were confiscated from students in such places as restrooms or hallways are displayed at Marshfield High School in Marshfield, Mass.

—Steven Senne/AP

The new CDC study, released Thursday, found high school vaping was at about the same level last year as it was in 2016, about 11 percent. That translates to about 1 in 9 students, meaning it continued to be the most commonly used product.

Cigarette use continued to fall, though slightly, and last year dropped into a tie with cigars for second place. That marks the first time cigars have been smoked as commonly as cigarettes among children.

Among middle schoolers, about 1 in 30 said last year that they had recently vaped. That was a decrease from the year before, when the figure was about 1 in 23.

Brian King, who oversees the CDC’s tobacco survey work, said he believes the survey captures a sizable proportion of kids who are using Juul e-cigarettes, but he acknowledged there could be “some under-estimation.” He said there are plans to add questions about Juul, but those likely won’t appear until next year’s survey.

Similar plans are being made for an annual University of Michigan survey of adolescent tobacco use, said Richard Miech, who leads that study. Because kids currently aren’t being asked about Juul specifically, researchers can’t say for sure if vaping is increasing or decreasing, he said.

Juul e-cigarettes first went on sale in 2015. They look like computer flash drives, can be recharged in computer USB ports, and have prefilled cartridges containing nicotine. They also offer kid-friendly flavors like fruit and creme brulee, and teens can smoke them discreetly, even in class.

Last year, Juul became the top-selling e-cigarette brand, with more than $650 million in retail sales. That’s due at least partly to aggressive marketing through Instagram and other social media, Huang noted in a recent article in the journal Tobacco Control.

More data is needed to see how much of those sales were to kids, he said in an interview.

“But looking at the sales data, I think it’s hard to say the use of e-cigarettes among teens is steady or declining,” he said.

The U.S. Food and Drug Administration has been targeting Juul. In April, the agency issued warnings to retailers about sales to children. The FDA also asked the manufacturer, Juul Labs of San Francisco, to turn over documents about the devices’ design and marketing.

Juul Labs has said it’s trying to combat teen use of its products. Company officials this week said they are launching a new ad campaign aimed at answering parents’ questions about the devices.